CVE-2022-50535

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Fix potential null-deref in dm_resume

[Why]
Fixing smatch error:
dm_resume() error: we previously assumed 'aconnector->dc_link' could be null

[How]
Check if dc_link null at the beginning of the loop,
so further checks can be dropped.